Field of the Invention
The present invention relates to a method for driving a field-effect transistor having a source section, a drain section and a gate section, which includes applying a gate voltage to the gate section and causing the formation and/or maintenance of an electrically conductive channel between the source section and the drain section.
Such field-effect transistors (FETS) and methods for driving them have been known for a long time. FIG. 4 shows a practical embodiment of such a transistor which is described below.
In the case of conventional field-effect transistors in steady-state operation, it is not possible to pass a voltage applied to the source or drain section through a gate voltage which is of equal magnitude or is lower. In fact, for that purpose the gate voltage must be changed to a level which is above the voltage to be passed through by an amount at least equal to a material-dependent threshold voltage for channel formation.
Particularly in digital technology, where field-effect transistors of the enhancement type are predominantly used, that is linked with not inconsiderable difficulties when it is intended to switch voltage levels which are above the supply voltage. The production of an additional voltage level for use as the gate voltage has until now been carried out through the use of so-called pumps, which raise a voltage at a low level (in steps if necessary) to a voltage at a higher level. The circuitry implementation of such pumps necessitates a multiplicity of additional electronic components (in particular transistors and capacitors), which is disadvantageous, above all in the case of integrated circuits (it is area-intensive and high and low voltage surfaces are difficult to isolate).